I don't think its massively out. 0.75 bar of boost is only 11psi, thats only 4psi more than standard. It only takes for it to be overfuelling a little and that would cost it the 10-15bhp that I think it may have lost. The cooler will only make a significant difference at higher boost, the standard cooler can cool 9-10psi reasonably well.

If the turbo is in good condition, knowing that it has a full-width cooler, it could run 16 or maybe even 18psi. Even then, I'd only expect around 140bhp ATW or so.